The present invention generally relates to semiconductor chip assembly, and more specifically, to selectively soluble standoffs for semiconductor chip joining.
Solder pads can be used in the micro-electronics industry to make electrical and mechanical contacts or connections between integrated circuits (ICs) or between printed circuit boards (PCBs). Solder pads can also be used to make electrical and mechanical contacts or connections between optoelectronic and integrated photonic circuits and components.
To achieve such electrical and mechanical contacts and connections, the surfaces of two or more circuits to be connected can be coated with metal pads or pillars formed of one or more metals or metal films, such as titanium, nickel, copper, platinum, and/or gold, and also sometimes called Under-Bump Metallization pads (UBM pads).
Solder materials, such as tin, silver, gold, bismuth, indium or lead, can then be deposited on some of the metal pads on the substrate, using, for instance, electroplating to form a plated substrate. The surfaces of two circuits to be connected can thereafter be brought into close proximity or contact and then temperature can be temporarily elevated beyond the melting temperature of the solder material. When the solder materials are heated beyond the melting temperature, the melted solder can ball-up to minimize surface tension, contact a solder pad that is in close vertical proximity, wick this proximate or other adjacent solder pad and establish electrical contacts between the two circuits in close contact. Upon cooling, the solder can solidify to mechanically and electrically connect the two circuits.